I didn't think a 4MHz PIC would be fast enough to get a decent tone by toggling a pin in a loop, but I will definitely give it a try.
First, the SOUND command is toggling a pin in a loop, isn't it? Second, aren't you running the PIC at 8MHz? :-)

Let's do some quick back of an envelope calculations. On the 10F222 doing an AD conversion takes 13 CPU cycles (this does NOT include the time needed to charge the S/H capacitor but you're not allowing for any sample time at the moment so lets ignore that). In my code example we're doing two conversions per loop so 26 cycles. The other bit checking/flipping operations is, perhaps, 20 cycles. Lets call 50 instructioncycles so without any PAUSEUS at all in there it should do around 40kHz.

If you want the most out ouf it make sure you disable the WDT and tell the compiler about it, that will save a couple of cycles per loop.

The PAUSEUS is obviously there to slow it down and you'll need to play with the values to get the frequency to where you want it. We're doing two conversions per loop to keep the symetry so it should produce fairly Close to 50% dutycycle.

Give it a try and tell us how it works.

/Henrik.